This application is based on patent application No. 11-151270 filed in Japan, the contents of which is hereby incorporated by reference.
This invention relates to a printed circuit board testing apparatus for testing conductivity or open circuit and current leakage of a circuit pattern formed on a printed circuit board.
There have been proposed printed circuit board testing apparatus. They can be generally classified into two types in the aspect of test head:
(a) A first type of printed circuit board testing apparatus is provided with a dedicated test head to test an individual circuit pattern on a printed circuit board. The testing is executed by rendering contacts mounted on the test head to come into contact with certain points of circuit patterns on the printed circuit board. The contacts are activated in a specified order to test the conductivity of each circuit pattern.
(b) A second type of circuit board testing apparatus is provided with a test head having a pair of probes or movable contacts which move from one to another position depending on the circuit pattern on the printed circuit board to be tested. Such test head is hereinafter referred to as xe2x80x9cversatile-use test headxe2x80x9d, and is useable for testing a variety of circuit patterns. The second type of circuit board testing apparatus is disclosed in, for example, Japanese Unexamined Patent Publication No. (HEI) 3-229167 and Japanese Utility Model Unexamined Publication No. (HEI) 5-40893.
In the first type of circuit board testing apparatus, the dedicated test head is used only for particular printed circuit boards formed with the same circuit pattern. Accordingly, the time required for inspection or test of each printed circuit board is shortened if a large number of circuit boards having the same circuit pattern are to be tested. However, such dedicated test head designed specially for a particular printed circuit board needs a complicated production process, and approximately one week is required to produce one dedicated test head. Accordingly, this type of apparatus is suitable for testing a large number of printed circuit boards having the same circuit pattern at a time, but is not suitable for the case where a variety of printed circuit boards having different circuit patterns are tested one after another. In this type of apparatus, it is also required to keep a variety of dedicated test heads as a stock, and manage the status of stock to meet an expected repeated use for test of the particular printed circuit board.
Furthermore, recent years have seen an advanced technology of forming a very fine circuit pattern on a printed circuit board. Therefore, it becomes technically difficult to produce a dedicated test head capable of testing circuit boards having such very fine circuit patterns because adjacent contacts are required to be located at a very small space.
The second type of circuit board testing apparatus is adapted for general or versatile use. In this type of apparatus, a pair of probes or movable contacts are moved over the printed circuit board in accordance with pre-stored program data for testing. The program data for controlling the movement of contacts can be programmed more easily than programming Computer Aided Design (CAD) data for making a circuit pattern. This type of apparatus does not require production of a dedicated test head having a complicated configuration for individual circuit patterns of a printed circuit board. Despite the fact that the second type of apparatus needs a longer time for testing of each printed circuit board than the first type of apparatus, the second type of apparatus is advantageous in testing a small number of printed circuit boards for trial when, for example, prototype printed circuit boards are manufactured.
The two types of apparatus have their respective advantageous features and disadvantageous features, which have not sufficiently responded to a variety of requirements or demands in the inspection and testing operation. Also, it has been undesirable in the aspect of cost-effectiveness and installation space to equip the two types of apparatus.
It is an object of the present invention to provide a printed circuit board testing apparatus which is free from the problems residing in the prior art.
According to an aspect of the invention, a printed circuit board testing apparatus comprises a table for supporting a printed circuit board formed with a circuit pattern thereon, and a test head holding portion for holding a dedicated test head and a versatile-use test head in such a position as to face the circuit board supported on the table. The dedicated test head includes a plurality of fixed contacts. The versatile-use test head includes a pair of movable contacts movable independently from each other.
These and other objects, features and advantages of the present invention will become more apparent upon a reading of the following detailed description and accompanying drawings.